Two microorganisms, namely, Moniliella tomentosa var. pollinis CBS461.67 and Aureobasidium sp. SN-G42 FERM P-8940, are known currently to be employed practically to produce erythritol.
The former is employed, for example, in methods for producing polyols in an industrial scale by means of fermentation of saccharides (Japanese Patent Publication No. 6-30591 (30591/1994), ibid. 6-30592 (30592/1994), ibid. 6-30593 (30593/1994), ibid. 6-30594 (30594/1994)), and in these publications methods for producing a series of polyols including erythritol are disclosed.
However, the strain of Moniliella tomentosa var. pollinis employed in such methods has a poor saccharide resistance and suffers from reduced yield of erythritol at a high saccharide concentration. Thus, at the saccharide concentration of 25 w/v % the saccharide-based erythritol yield (amount of erythritol produced relative to the amount of saccharide consumed) is as high as 42%, but at the saccharide concentration as high as 35 w/v % the saccharide-based erythritol yield is 33%, and at 40 w/v % the yield is as markedly low as 27%.
On the other hand, the latter is disclosed in Japanese Patent Publications 4-11189 (11189/1992) and ibid. 4-635 (635/1992) in which a microorganism having an erythritol producing ability and a method for producing erythritol by means of fermentation using such microorganism are described.
The microorganism employed in such method has an excellent saccharide resistance and an excellent erythritol producing ability. However, since this strain exhibits extensive growth, separation of the cells from the fermentation fluid in the process of purification of erythritol in an attempt to conduct a mass production requires a prolonged period of time and resulting large amount of waste cells can not easily be disposed.
Trichosporonoides oedocephalis employed in the present invention was reported by R. H. Haskins (Canadian Journal of Botany, Volume 45, p. 515-520, 1967) with regard to its microbiological characteristics and its ability of producing erythritol. However, this report contained no description of the yield of erythritol.
In addition, a microorganism belonging to genus Trichosporonoides was reported by Marina A. Y. Aoki in Campinus University in Brazil (Biotechnology Letters, Volume 15, No.4, p.383-388, April 1993) to be employed in conversion from sucrose and glucose to erythritol, although the species is not known. According to this report, the rates of conversion from glucose to erythritol and sucrose to erythritol were as relatively high as 43.0% and 37.4%, respectively, but the saccharide concentration for such yields was as low as 10 w/v %, indicating a poor applicability to a production in an industrial scale.